It has been proposed to meter and dispense fluids with the help of a pump, the piston of which sucks up the required quantity of the fluid and then expels this quantity in a subsequent operation. For this, complicated valve systems have been proposed for exact control of the two working-cycles and for ensuring precise metering. However, liquids and thermoplastic melts of high viscosity are not easy to meter in this way, especially those which have a strong tendency to stringiness if one tries to divide them into single small portions. Permanently-tacky melt-adhesives for example are particularly difficult to handle.
By "permanently-tacky melt-adhesives" we mean those adhesives which can be applied in hot, molten form, and which in dry form (free from solvent), at room-temperature and on mere contact, solidly adhere to a number of different surfaces. These adhesives do not require activation by water, solvent or heat in order to give them a strong adhesion to the most widely-differing materials, such as paper, cellophane, glass, wood and metal. When they are applied on a suitable backing-substance, they can be pulled off without resistance from smooth underlays. These materials are thus normally kept and transported in siliconized containers until the moment of processing. Hitherto it has not been possible to granulate them like other hot melt-adhesives for storage and transport in drums or sacks.